Abstract : Launch plume imagery and ground HCl measurements were accomplished during the launch of Titan IV Mission #K2 at Cape Canaveral Air Station on 3 July 1996. These data will be used to improve the accuracy of the Rocket Exhaust Effluent Diffusion Model. The imagery from three sites (integrated IR and visible imagers at each) showed a cloud stabilization height of 1871 m (72% higher than predicted), reached in 10-14 min (4% to 46% longer than predicted). The cloud trajectory was east-northeasterly, similar to prediction, and the 6.2 m/s speed was 44% faster than predicted. Aircraft HCl measurements were not taken for this launch. Ground dosimeters around the launch pad measured dosages as high as 378 ppm min.